JP2006140377A - Sheet-form circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high reliability sheet-form circuit board, having a large degree of freedom of its design which so radiates and so heat-dissipates as infrared rays the heat generated from a heat-generating element formed on a resin substrate as to increase its rated power. <P>SOLUTION: The sheet-form circuit board includes a sheet substrate 12 made of an infrared-ray transmitting resin, and includes a heat-radiating thin-film layer, installed between the sheet substrate 12 and a heat-generating element 22 formed on the sheet substrate 12. Further, the heat-radiating thin-film layer is constituted out of at least two layers, which comprise a first heat transferring film 18 so formed as to contact with the heat generating element 22 and comprise a heat-radiating film 20 so formed as to contact with the sheet substrate 12 and having a shape at least larger than the first heat transferring film 18. Moreover, the first heat transfer film 18 is an insulating film, having the same shape as that of the heat-generating element 22 and having a large thermal conductivity and a large film thickness. Furthermore, the heat radiating film 20 is constituted of a material whose emissivity is at least larger than that of the first heat transfer film 18 in the infrared-ray transmission range of the sheet substrate 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thin film element formed on a sheet substrate made of a resin, and more particularly to a sheet-like circuit substrate that operates stably even when large electric power is applied by improving the heat dissipation of a heat generating element.

  Circuit boards used in various electronic devices are mainly passive parts such as capacitors, resistors, inductors, semiconductor elements, etc. on printed wiring boards (hereinafter referred to as PWB) in which copper wiring patterns are formed on glass cloth epoxy resin. The active parts are mounted by solder reflow or the like to form an electronic circuit.

  2. Description of the Related Art In recent years, portable electronic devices represented by mobile phones have been downsized and highly functional, and miniaturization of wiring patterns, passive components, and active components has progressed in order to accommodate complex circuits in as small an area as possible. .

  However, the configuration of the circuit board on which passive components and the like are mounted on the PWB cannot cope with the downsizing of such portable electronic devices. That is, the thickness of a normal PWB or passive component is approximately 0.3 mm to 1.0 mm, and the total thickness after mounting on the PWB is approximately 0.6 mm to 2.0 mm. With such a thickness, the electronic device is hindered from being thinned. In addition, since it is difficult to bend the circuit board, it is difficult to arrange the circuit board freely in a three-dimensional manner, and the degree of freedom in designing the casing of the electronic device is restricted. For this reason, a circuit board having flexibility is required. On the other hand, there is a circuit board in which a copper wiring pattern is formed using a sheet substrate such as a polyimide film. If this is used, it can be bent and placed in the electronic device, so that the electronic device can be downsized.

  However, most circuit boards using current flexible sheet substrates have a configuration in which only a wiring pattern is formed, or passive components and active components are mounted. Therefore, even if a thin sheet substrate is used, the overall thickness cannot be reduced if passive components or the like are mounted.

  As described above, the circuit board is required to be thin, bendable, and highly functional. In response to this requirement, a thin and flexible sheet-like circuit board is produced by forming passive components mainly on a sheet substrate using a flexible polyimide film by thin film technology or thick film printing technology. A method has been proposed.

  For example, in a non-contact IC card or the like, it is necessary to make the thickness of the card as very thin as 1 mm or less, and it is required to make the passive component as thin as possible from about several hundred microns. Yes. For this reason, a structure and a manufacturing method of a thin film capacitor formed by a thin film method are shown. This thin film capacitor is composed of an organic polymer substrate with an external electrode, an internal counter electrode, a dielectric, and an external electrode. The external electrode is not in contact with the internal counter surface and the outer periphery. It has a structure in which an external electrode is formed inside. Thereby, a micrometer order thin film capacitor can be formed, and a flexible thin film capacitor that does not break can be manufactured (for example, see Patent Document 1).

  In addition, sheet-like circuit boards that can be bent and reduced in characteristics and reliability deterioration of circuit elements formed by thin film technology by reducing irregularities on the surface of the flexible board and preventing intrusion of gas such as moisture The manufacturing technique of is also disclosed. This sheet-like circuit board is formed by forming a circuit element constituting an electric circuit on a flexible substrate made of an organic polymer, and is a first circuit provided between the circuit element and the flexible substrate. It has an inorganic protective film and a second inorganic protective film that covers the circuit element, and the first inorganic protective film and the second inorganic protective film have a configuration formed only in a region where the circuit element is formed. (For example, refer to Patent Document 2).

  A circuit board can be made very thin by forming a thin film element on a sheet substrate using a thin film technique or a thick film printing technique as in the above example. However, in such a circuit board configuration, when a heat generating element having a characteristic of generating heat by current such as a thin film element, such as a thin film resistor, is formed, the sheet substrate is made of resin, so the thermal conductivity is poor. It is difficult to quickly and efficiently dissipate the heat generated by the exothermic element. For this reason, with thin film resistors that generate heat when energized, if the heat dissipation is poor, the rated power must be limited to the extent that the heat generation does not affect the circuit, and the circuit design is very limited. .

On the other hand, in the ceramic substrate, a configuration for efficiently dissipating heat when a heating element such as a semiconductor element is mounted is disclosed. A ceramic substrate has a property that heat is easily diffused in the front and back directions, but heat is hardly transmitted in the lateral direction of the substrate. For this reason, in the area where the heat generating elements of the ceramic substrate are mounted, a plurality of wiring layers made of conductors spread radially with a step below the heat generating elements, and the plurality of wiring layers are conducted through the through holes. The through hole is filled with a refractory metal. Thermal conductivity can be increased by using a conductor such as tungsten in the empty space on the back side of the element that generates a large amount of heat, a wiring layer, and a through hole, and heat from the heating element can be efficiently dissipated (for example, (See Patent Document 3).
JP 2000-106324 A Japanese Patent Laid-Open No. 2004-22788 JP 2001-77540 A

  In the third example, a wiring layer is formed in order to increase the lateral heat conduction with respect to the ceramic substrate, heat is transmitted through the wiring layer, and heat is radiated through the ceramic substrate. Since the ceramic material has a much higher thermal conductivity than the resin material, heat can be dissipated well by contacting the ceramic substrate with a housing or the like.

  On the other hand, in the case of a sheet substrate made of resin, even if a wiring layer is provided and heat is transmitted in the lateral direction as in the above example, the thermal conductivity of the sheet substrate itself, which is resin, is small, so It is not possible to sufficiently dissipate heat. Furthermore, the ceramic substrate can be easily brought into close contact with a housing or the like or through a heat dissipation sheet. However, the sheet substrate is often used by being folded so that it can be stored in the space inside the housing, and it is difficult to make the sheet substrate adhere to the housing like a ceramic substrate.

  In addition, when a wiring layer is formed below the thin film element as in the third example, an insulating layer for insulating the wiring layer and the thin film element has to be further formed, which only complicates the process. In addition, there is a problem that the manufacturing yield is reduced and the cost of the circuit board is increased.

  In the present invention, among thin film elements formed on a sheet substrate made of resin, heat generated from a heat-generating element that generates heat when energized is radiated as infrared rays to dissipate it, so that the rated power can be increased and the degree of freedom in design. An object of the present invention is to provide a sheet circuit board having a large size and high reliability.

  In order to solve the above problems, a sheet-like circuit board of the present invention generates heat by energizing a sheet substrate made of a resin that transmits infrared light, a thin film element formed on the sheet substrate, and the thin film element. A heat-dissipating thin film layer provided between the heat-generating element and the sheet substrate, the heat-dissipating thin-film layer formed in contact with the first heat-conductive film formed in contact with the heat-generating element and the sheet substrate. The heat radiation film having at least a two-layer structure having at least a larger shape than the first heat conduction film. The first heat conduction film is an insulating film having at least the same shape as the exothermic element. The sheet substrate has a configuration using a material having an emissivity at least higher than that of the first heat conductive film in the infrared light transmission range.

  With this configuration, the heat generated in the heat generating element is efficiently transmitted to the first heat conductive film, and further transmitted from the first heat conductive film to the heat radiation film. The heat radiation film rises in temperature due to this heat, and radiates infrared rays generated according to the temperature into the air via the sheet substrate. Since this thermal radiation film has an emissivity that is at least greater than that of the first thermal conductive film, more infrared rays can be radiated to the outside and radiated as compared with thermal radiation from the first thermal conductive film. As a result, it is possible to efficiently dissipate the heat generated in the heat generating element as infrared radiation.

Thermal radiation is a phenomenon in which a substance converts thermal energy into electromagnetic waves such as infrared rays and emits it. Therefore, in order for the heat radiation film to efficiently radiate electromagnetic waves such as infrared rays, not only the emissivity of the heat radiation film is large, but also the heat conduction from the first heat conduction film to the heat radiation film is good, In addition, it is desirable that the entire surface of the heat radiation film be uniformly heated in a short time. In the present invention, since the infrared rays generated in the heat radiation film are transmitted through the sheet substrate and radiated into the air to dissipate heat, the emissivity in the infrared light transmission range of the sheet substrate is at least the first heat conduction. It is also required that the material be larger than the membrane. As a specific emissivity of such a heat radiation film, it is desirable to use a material of 0.8 or more, and more desirably a material of 0.9 or more. Examples of materials having an emissivity of 0.8 or more include zirconia (ZrO ₂ ), a mixture of silicon oxide and alumina (a mixture of SiO ₂ and Al ₂ O ₃ ), magnesia (MgO), magnesia, alumina, and oxidation. A silicon mixture (a mixture of MgO, Al ₂ O ₃ and SiO ₂ ) or the like may be formed by sputtering. Further, a carbon thin film, a thin film of reduced titanium oxide, or a mixed thin film of aluminum nitride and aluminum oxide (a mixed thin film of AlN and Al ₂ O ₃ ) may be used. These materials have an emissivity of 0.8 or more in the infrared light range of about 7 μm or more, which is the transmission wavelength of the sheet substrate. Furthermore, in the case of a thermal radiation film having an emissivity of 0.9 or more, a method of forming a blackened film in which carbon or the like is mixed with the above material or a minute unevenness is formed on the surface of the sheet substrate. It can be manufactured by a method of forming a film after increasing the surface area.

  In addition, since the thickness of the first heat conductive film can be increased, the heat capacity can be increased. Therefore, even if the electric power supplied with respect to a heat generating element is enlarged, the temperature rise as a whole can be suppressed. Further, even if the heat generating element generates heat locally, the heat conductivity of the first heat conductive film is large, and therefore it can be diffused uniformly and quickly throughout the first heat conductive film. It is also possible to suppress the local temperature rise. The sheet substrate is made of a resin that transmits infrared light. For example, a polyimide film is used. However, a substrate made of such a resin has good transparency to infrared light, and is therefore generated in the heat radiation film. Infrared light can be emitted into the air without being absorbed by the sheet substrate.

  Further, in the above configuration, the heat generating element is a thin film resistor, the first heat conductive film is formed in contact with the thin film resistor, and has the same shape as the resistive film, and the film thickness is thicker than the resistive film. In addition, the structure may be thinner than the connection electrode connected to the resistance film.

  With this configuration, even if a large amount of power is applied to the thin film resistor that is a heat-generating element, an increase in temperature can be suppressed. Further, by making the thickness of the first heat conductive film thicker than the resistance film and thinner than the connection electrode, it is possible to prevent the occurrence of connection failure between the connection electrode and the resistance film while increasing the heat capacity. Further, the heat radiation film may have the same shape as the resistance film. In that case, the heat radiation film, the first heat conduction film, and the resistance film can be successively formed in this order in the same vacuum apparatus, and the manufacturing process can be simplified.

  Further, in the above configuration, the heat generating element is a thin film resistor, and the thin film layer for heat dissipation is a second heat conductive film having a larger shape than the first heat conductive film between the first heat conductive film and the heat radiation film. The shape of the heat radiation film may be the same as or more than the shape of the second heat conductive film.

  With this configuration, the heat generated in the resistance film can be efficiently diffused between the first heat conductive film and the second heat conductive film. Thereby, the temperature of the heat radiation film rises almost uniformly over the entire surface, so that it can be radiated and dissipated as infrared rays from the entire surface. Further, the two-stage configuration of the first heat conductive film and the second heat conductive film can prevent the occurrence of poor connection between the connection electrode and the resistance film. Further, the first heat conductive film can be continuously formed with the same vacuum apparatus as the resistance film.

  Further, in the above configuration, a resin protective film that covers the heat generating element is formed above the heat generating element, and the emissivity in the infrared light range of the resin protective film is at least higher than the emissivity of the first heat conductive film. A configuration using a large material may be used.

  With this configuration, the heat generated by the heat generating element can be radiated as infrared rays also from the resin protective film formed on the upper part of the heat generating element. Can be realized. The resin protective film is preferably made of a material having a high thermal conductivity and an emissivity in the infrared light range that is at least greater than the emissivity of the first thermal conductive film. By using such a material, infrared radiation can be efficiently emitted from the resin protective film to dissipate heat. Moreover, since the heat from the heat generating element is transferred to the resin protective film by heat conduction, it is also desirable that the material has a high heat conductivity. For example, as a resin, polyester resin, urethane resin, acrylic resin, epoxy resin, melamine resin, vinyl chloride resin, etc. are used, and a paste in which fine particles such as carbon and silicon carbide are dispersed in this resin is printed. It may be formed on the exothermic element by a known method.

  The method for producing a sheet-like circuit board according to the present invention includes a step of roughening a surface of a sheet substrate made of a resin that transmits infrared light, and an infrared light of the sheet substrate on the roughened sheet substrate. Forming a heat radiation film having an emissivity at least larger than the emissivity of the first heat conductive film in the transmission range, and a heat dissipation thin film layer formed by laminating the first heat conductive film on the heat radiation film; And a step of forming a heat generating element on the first heat conductive film.

  By setting it as such a method, since the surface of the sheet | seat board | substrate is roughened, the surface area of a thermal radiation film | membrane increases and it can improve an infrared emissivity. As a result, the heat dissipation efficiency can be increased. As a roughening method, for example, a method of forming a minute unevenness on the surface of the sheet substrate by arranging the sheet substrate in a vacuum apparatus and irradiating ions is desirable. Since the rough surface by this method can form very minute irregularities uniformly, a thin film element having good reproducibility and stable characteristics can be formed on a sheet substrate.

  Further, in the above method, a second heat conductive film having a larger shape than the first heat conductive film is further formed between the first heat conductive film and the heat radiation film as the heat radiation thin film layer, The shape may be formed to be equal to or more than the shape of the second heat conductive film.

  By such a method, the heat generated in the exothermic element can be radiated more efficiently.

  Moreover, in the said method, it is good also as a method of forming further the resin protective film whose emissivity in an infrared-light range is more than the heat emissivity of a 1st heat conductive film so that a heat generating element may be covered. By forming the resin protective film having such characteristics, not only heat can be radiated through the sheet substrate but also heat can be radiated through the resin protective film, so that the heat radiating characteristics can be further improved.

  The sheet-like circuit board of the present invention has a thin film layer for heat dissipation between a heat generating element that generates heat when energized among thin film elements formed on a sheet substrate made of a resin that transmits infrared light, and the sheet substrate. It is a structure to dissipate heat by radiating heat transmitted to the thin film layer for heat dissipation by heat conduction from the heat radiation film into the air through the sheet substrate as infrared rays. Thereby, since a large electric power can be applied to the heat-generating element, there is a great effect that it is possible to realize a thin sheet-like circuit board having high functionality while having flexibility.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, since the same code | symbol is attached | subjected about the same component, description may be abbreviate | omitted.

(First embodiment)
FIG. 1 is a diagram showing an example of a configuration of a sheet-like circuit board 10 according to the first embodiment of the present invention. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along the line AA.

  In the present embodiment, as an example, a thin film resistor 22 is formed as a sheet-like circuit board 10 on a sheet substrate 12 made of a resin, for example, a polyimide film, as a heat generating element that generates heat when energized. Will be described.

  In the present embodiment, the heat radiation film 20, the first heat conductive film 18, and the resistance film 14 are formed in this order on the sheet substrate 12. Moreover, the heat radiation film 20, the first heat conductive film 18, and the resistance film 14 have the same shape. The first thermal conductive film 18 has a thermal conductivity larger than that of the resistance film 14 and is thicker than the resistance film 14, but is thinner than the thicknesses of the connection electrodes 16a and 16b provided on both sides. The thin film layer for heat dissipation refers to the first heat conductive film 18 and the heat radiation film 20 in the present embodiment. The connection electrodes 16a and 16b and the resistance film 14 formed on both sides constitute a thin film resistor 22. Further, the connection electrodes 16a and 16b are also a part of the wiring pattern 16, and the wiring pattern 16 is used to simultaneously connect to connection terminals of external devices and other thin film elements (not shown) on the sheet substrate 12. Yes.

  With the above configuration, the sheet-like circuit board 10 of the present embodiment has the first heat conductive film 18 that is a hard thin film formed in the same shape as the resistance film 14, and thus has sufficient flexibility. Can be held. In addition, heat generated by the thin film resistor 22 that is a heat generating element can be efficiently radiated as infrared radiation. Therefore, it is effective when folded and housed in a casing or the like of a portable electronic device.

  A method for manufacturing the sheet-like circuit board 10 of the present embodiment will be described below. First, a metal mask provided with an opening having the same shape as that of the resistance film 14 is adhered and fixed on the sheet substrate 12. After the sheet substrate 12 to which the metal mask is closely fixed is placed at a predetermined position in the vacuum apparatus, the heat radiation film 20, the first heat conductive film 18 and the resistance film are formed by using a film forming method such as vacuum deposition or sputtering. Are sequentially formed in this order.

  Next, a metal thin film such as aluminum (Al) is formed on the wiring pattern 16 by a common film formation method such as vacuum evaporation or sputtering. This wiring pattern 16 can also be formed with a predetermined pattern at the same time as film formation using a metal mask. Alternatively, after forming a metal thin film on the entire surface of the sheet substrate 12, it may be processed by a photolithography process and an etching process.

  Thereby, the sheet-like circuit board 10 provided with the thin film resistor 22 having a shape and a resistance value set in a preset position on the sheet substrate 12 is obtained.

  Next, these materials will be described.

The heat radiation film 20 has a large emissivity in the infrared light transmission range of the sheet substrate 12 and a high adhesion to the sheet substrate 12, and further, the temperature rises in a short time due to heat from the first heat conductive film 18. Therefore, it is desirable to use a material having a relatively high thermal conductivity. For example, zirconia (ZrO ₂ ), a mixture of silicon oxide and alumina (a mixture of SiO ₂ and Al ₂ O ₃ ), magnesia (MgO), a mixture of magnesia, alumina and silicon oxide (MgO, Al ₂ O ₃ and SiO ₂ ) and the like may be formed by sputtering. Further, a carbon thin film, a thin film of reduced titanium oxide, or a mixed thin film of aluminum nitride and aluminum oxide (a mixed thin film of AlN and Al ₂ O ₃ ) may be used. These materials have an emissivity of 0.8 or more in the infrared light range of about 7 μm or more, which is the transmission wavelength of the sheet substrate 12. Moreover, since these materials have a higher thermal conductivity than the resin that is the sheet substrate 12, the temperature immediately rises upon receiving heat from the first thermal conductive film 18, and radiates infrared rays corresponding to the temperature, Heat can be dissipated. The thickness of the heat radiation film 20 is not particularly limited.

Furthermore, the thermal radiation film 20 may be a thin film obtained by mixing not only the above materials but also a material having a high emissivity and a material having a high thermal conductivity. For example, sputtering is performed on the sheet substrate 12 using a target in which zirconia (ZrO ₂ ), which is a material having a high emissivity, and silicon carbide (SiC) or aluminum nitride (AlN), which has a high thermal conductivity, are mixed at a predetermined ratio. The heat radiation film 20 may be formed. With such a method, the heat radiation film 20 having a high emissivity and thermal conductivity can be obtained, and the film formation method is simple, so productivity is not hindered.

  Further, if the surface of the sheet substrate 12 is treated with, for example, oxygen plasma before forming the thermal radiation film 20, fine irregularities can be formed on the surface of the sheet substrate 12, so that after such fine irregularities are provided The heat radiation film 20 may be formed. Even if such fine irregularities are provided, the emissivity of the thermal radiation film 20 can be further increased without causing a particularly large effect on the characteristics of the thin film resistance.

Next, the first heat conductive film 18 is required to be insulative in order to be formed in contact with the resistance film 14. Furthermore, it is desirable that the thermal conductivity is larger than that of the resistance film 14 and the coefficient of thermal expansion is a value close to that of the resistance film 14. As such a material, a nitride thin film or a carbide thin film such as aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), or silicon carbide (SiC) can be used.

Furthermore, an oxide thin film such as aluminum oxide (Al ₂ O ₃ ) may be used. Note that silicon nitride does not have to be a thin film having a stoichiometric composition. Further, in the case of silicon carbide, a hydrogenated silicon carbide film can be obtained by adding hydrogen to the discharge gas when the film is formed by sputtering, for example. Since this hydrogenated silicon carbide has a very high resistance, it is suitable as the first thermal conductive film 18. Further, as in the case of the heat radiation film 20, the first heat conductive film 18 may be formed by sputtering by mixing materials having high heat conductivity. With such a method, the first heat having a large thermal conductivity while providing insulation can be obtained by mixing an insulating material even if it is a material that cannot be used because it has electrical conductivity by itself. The conductive film 18 can be easily obtained.

  Since the first thermal conductive film 18 using such a material has a high thermal conductivity and has an insulating property, when it is formed below the resistive film 14, the heat generated in the resistive film 14 is quickly transmitted. heat. In general, the heat generated in the resistance film 14 is not generated uniformly in the entire film and is likely to generate heat locally. Even when such local heat generation occurs, the first heat conductive film 18 quickly diffuses and becomes uniform. As a result, deterioration of the resistance film 14 can be suppressed.

The resistance film 14 is not only a single material such as a nichrome alloy (Ni—Cr) or tantalum nitride (Ta ₂ N) but also a material generally used as a thin film resistor such as a mixed film of metal and oxide. Is possible. A material for the resistance film 14 is selected according to the resistance value of a thin film resistor to be manufactured. However, when a high resistance value is required, it is generally handled by reducing the film thickness. For this reason, deterioration due to heat generation is more likely to occur in thin film resistors having higher resistance values.

  In addition, although the thermal radiation film | membrane 20, the 1st heat conductive film 18, and the resistance film 14 demonstrated the method of pattern-forming simultaneously with film-forming using a metal mask, it is not limited to this method. For example, after the thermal radiation film 20, the first thermal conductive film 18, and the resistance film 14 are continuously formed on the entire surface of the sheet substrate 12, a photolithography process and an etching process are performed to obtain a predetermined shape as illustrated. It may be processed.

  In addition, the wiring pattern 16 including the connection electrodes 16a and 16b as a part thereof includes aluminum (Al), nickel (Ni), platinum (Pt), gold (Au), palladium (Pd), copper (Cu), and tantalum ( Not only a single layer film such as Ta), titanium (Ti) or molybdenum (Mo) can be used, but also a laminated film of these layers may be used. For example, a Ti—Cu bilayer configuration film in which a titanium (Ti) film is formed on the lower layer side and a copper (Cu) film is formed on the upper layer may be used. With such a film configuration, adhesion with the sheet substrate can be improved and connection with other substrates can be facilitated. In many cases, an electrode terminal (not shown) is provided at a predetermined position of the wiring pattern 16 for connection to an external device. This electrode terminal is formed by plating, for example, and a solderable electrode terminal can be obtained by forming a copper (Cu) film and a gold (Au) film on the copper (Cu) film.

  In the present embodiment, a polyimide film has been described as an example of the sheet substrate 12, but the present invention is not limited to this. For example, a resin such as a polyester film or a polyethylene terephthalate film, which has infrared transmission characteristics and has an insulating property, can be used without any particular limitation.

  Hereinafter, an example in which the power that can be input when the sheet-like circuit board 10 of the present embodiment (hereinafter referred to as Example 1) and the thin film layer for heat dissipation are not provided below the resistance film is compared will be described. Hereinafter, this is referred to as Comparative Example 1. In Example 1 and Comparative Example 1, the material, shape, thickness, and the like of the sheet substrate, the resistance film, and the wiring pattern were the same. Therefore, the difference between Comparative Example 1 and Example 1 is only the presence or absence of the thin film for heat dissipation under the resistance film. About Example 1 and Comparative Example 1 produced in this way, electricity was passed through the wiring pattern, and the relationship between the current value and the occurrence of burnout was examined. As a result, it was confirmed that even if the current value in Example 1 was about 20 times larger than the current value when Comparative Example 1 burned out, no burning or the like occurred. It was also confirmed that as the resistance film was made thinner in order to increase the resistance value, the improvement effect compared with Comparative Example 1 was increased.

  In the present embodiment, only the thin film resistor 22 is described as an example of the heat generating element. However, a plurality of such thin film resistors may be included, and such a thin film resistor and a capacitor or a thin film resistor and a capacitor are included. And a sheet-like circuit board including an inductor and the like. In the present embodiment, the configuration in which the protective film is not formed on the surface of the thin film resistor has been described. However, a protective film that covers the thin film resistor may be formed. As the protective film, for example, thermosetting or ultraviolet curable polyimide resin, epoxy resin, or silicone resin can be used.

(Second Embodiment)
FIG. 2 is a plan view and a cross-sectional view for explaining the configuration of the sheet-like circuit board 30 according to the second embodiment of the present invention. 2A is a plan view, FIG. 2B is a cross-sectional view taken along line BB shown in FIG. 2A, and FIG. 2C is a cross-sectional view taken along line CC shown in FIG. FIG.

  In the present embodiment, the heat radiation film 42, the second heat conduction film 40, the first heat conduction film 38, and the resistance film 34 constituting the thin film resistor which is a heat-generating element are formed in this order on the sheet substrate 32. Has been. Further, the heat radiation film 42 and the second heat conduction film 40 have the same shape, and similarly, the first heat conduction film 38 and the resistance film 34 have the same shape. Further, the first thermal conductive film 38 is made of a material having a higher thermal conductivity than that of the resistance film 34, and the thickness thereof is thicker than that of the resistance film 34 and is thinner than the thicknesses of the connection electrodes 36a and 36b provided on both sides. ing. Similarly, the second heat conductive film 40 is also formed thinner than the connection electrodes 36a and 36b. In the present embodiment, the heat radiation thin film layer includes a first heat conductive film 38, a second heat conductive film 40, and a heat radiation film 42.

  The thin film resistor 24 is constituted by the connection electrodes 36a and 36b and the resistance film 34 formed on both sides. Further, the connection electrodes 36a and 36b are a part of the wiring pattern 36, and the wiring pattern 36 is also connected to connection terminals of external devices and other thin film elements (not shown) on the sheet substrate 32.

  A method for manufacturing the sheet-like circuit board 30 of the present embodiment will be described below. First, a metal mask provided with an opening having the same shape as that of the heat radiation film 42 and the second heat conductive film 40 is adhered and fixed on the sheet substrate 32. After the sheet substrate 32 with the metal mask adhered and fixed is disposed at a predetermined position in the vacuum apparatus, the thermal radiation film 42 and the second thermal conductive film 40 are sequentially formed by using a film deposition method such as vacuum deposition or sputtering. Films are formed in this order. Thereby, the heat radiation film 42 and the second heat conductive film 40 having a predetermined shape are formed on the sheet substrate 32.

  Thereafter, another metal mask provided with an opening having the same shape as that of the resistance film 34 is firmly fixed to the sheet substrate 32. At this time, it arrange | positions so that the opening part of a metal mask may be located on the 2nd heat conductive film 40. FIG. Since the second heat conductive film 40 has a larger shape than the resistance film 34, it can be relatively easily aligned on the second heat conductive film 40. After the sheet substrate 32 to which the metal mask is closely fixed is arranged at a predetermined position in the vacuum apparatus, the first heat conductive film 38 and the resistance film 34 are formed in this order by using a film formation method such as vacuum deposition or sputtering. The film is formed. As a result, the first heat conductive film 38 and the resistance film 34 are formed on the second heat conductive film 40.

  Next, a metal mask having an opening having the same shape as the wiring pattern 36 is closely fixed to the sheet substrate. At this time, alignment is performed so that the connection electrodes 36 a and 36 b are connected to both ends of the resistance film 34. After the sheet substrate with the metal mask adhered and fixed is placed at a predetermined position in the vacuum apparatus, a metal thin film, for example, an aluminum (Al) thin film, which becomes the wiring pattern 36 is formed by using a film forming method such as vacuum deposition or sputtering. To do.

  The heat radiation film 42, the second heat conductive film 40, the first heat conductive film 38, the resistance film 34, and the wiring pattern 36 are not only formed by a metal mask as in the present embodiment, but also by a sheet substrate. After forming on the entire surface of 32, it may be produced by a method of processing each by a photolithography process and an etching process.

  The heat radiation film 42, the first heat conductive film 38, and the resistance film 34 may be the same as the materials and film thicknesses described in the first embodiment, and thus description thereof is omitted.

  The second heat conductive film 40 may be made of the same material as the first heat conductive film 38, or may be another material appropriately selected from the materials described in the first embodiment. In the present embodiment, the first heat conductive film 38 has the same shape as the resistance film 34, and its thickness is thicker than the resistance film 34 and thinner than the connection electrodes 36a and 36b. The second heat conductive film 40 is also formed thinner than the connection electrodes 36a and 36b. Therefore, no connection failure occurs between the resistance film 34 and the connection electrodes 36a and 36b. On the other hand, the heat generated in the resistance film 34 is diffused by the first heat conductive film 38 and further transmitted to the entire surface of the second heat conductive film 40. As a result, the heat radiation film in contact with the second heat conductive film 40 has a relatively uniform temperature rise on the entire surface, and infrared rays based on this temperature are emitted from the heat radiation film 42 through the sheet substrate 32 into the air. The heat is dissipated.

  As described above, in the present embodiment, in addition to the first heat conductive film having the same shape as the resistance film, a second heat conductive film having a shape larger than the first heat conductive film is formed, Since the heat radiation film is provided below the second heat conductive film, the amount of heat radiation can be further increased while preventing connection failure between the resistance film and the connection electrode. As a result, a stable and highly reliable sheet-like circuit board can be realized even when larger electric power is applied.

  Hereinafter, an example in which the available power is compared between the sheet-like circuit board 30 of the present embodiment (hereinafter referred to as Example 2) and Comparative Example 1 manufactured in the first embodiment will be described. In Example 2 and Comparative Example 1, the material, shape, thickness, and the like of the sheet substrate, the resistance film, and the wiring pattern were the same. Therefore, the comparative example 1 and Example 2 are the difference of the structure which provided the 1st heat conductive film, the 2nd heat conductive film, and the heat radiation film in the lower part of the resistance film. With respect to Example 2 and Comparative Example 1 produced in this way, the relationship between the current value and the occurrence of burnout was examined by energizing through the wiring pattern. As a result, it was confirmed that even when the current value in Example 2 was about 50 times larger than the current value when Comparative Example 1 burned out, no burning or the like occurred. Further, as the resistance film is made thinner in order to increase the resistance value, the improvement effect as compared with the comparative example 1 becomes larger as in the first embodiment.

  In the present embodiment, only the thin film resistor has been described as an example of the heat-generating element. However, a plurality of such thin film resistors may be included, and such a thin film resistor and capacitor, or a thin film resistor and capacitor, and A sheet-like circuit board including an inductor or the like may be used. In the present embodiment, the configuration in which the protective film is not formed on the surface of the thin film resistor has been described. However, a protective film that covers the thin film resistor may be formed. As the protective film, for example, thermosetting or ultraviolet curable polyimide resin, epoxy resin, or silicone resin can be used.

(Third embodiment)
3 and 4 are cross-sectional views for explaining the configuration of the sheet-like circuit boards 50 and 60 according to the third embodiment of the present invention. The sheet-like circuit board 50 of the present embodiment shown in FIG. 3 is at least larger than the emissivity of the first thermal conductive film in the region including the resistance film 14 of the sheet-like circuit board 10 described in the first embodiment. It is characterized in that a resin protective film 44 having an emissivity is formed.

  Further, the sheet-like circuit board 60 which is another configuration of the present embodiment shown in FIG. 4 has a first heat conduction in the region including the resistance film 34 of the sheet-like circuit board 30 described in the second embodiment. The resin protective film 46 having an emissivity at least larger than the emissivity of the film is formed.

  The resin protective films 44 and 46 are preferably made of a material having a high thermal conductivity and an emissivity of 0.8 or more. If the emissivity is 0.9 or more, the method heat efficiency is further improved, which is desirable. Moreover, since the heat from the heat generating element is transmitted to the resin protective films 44 and 46 by heat conduction, it is also desirable that the material has a high heat conductivity. In the present embodiment, for example, an epoxy resin is used, and a resin in which fine particles of carbon are dispersed in this resin is pasted, applied only to a region near the resistance films 14 and 34 with a dispenser, and cured by heating. It was.

  With such a configuration, heat radiation from the resin protective films 44 and 46 is generated simultaneously with the heat radiation through the sheet substrates 12 and 32, so that a larger electric power can be applied and the degree of freedom in circuit design. Large sheet-like circuit board can be realized.

  In the present embodiment, only the thin film resistors 22 and 24 are described as examples of the heat generating element. However, a plurality of such thin film resistors may be included, and such a thin film resistor and a capacitor or a thin film resistor may be included. And a sheet-like circuit board including a capacitor and an inductor. In the present embodiment, the configuration in which the protective film is not formed on the surface of the thin film resistor has been described. However, a protective film that covers the thin film resistor may be formed. As the protective film, for example, thermosetting or ultraviolet curable polyimide resin, epoxy resin, or silicone resin can be used.

  Thus, by forming the resin protective film only in the region of the thin film resistor that is a heat generating element, flexibility can be maintained while further improving the heat dissipation by heat radiation.

  In the first embodiment and the second embodiment, the protective film is not formed on the surface of the resistance film of the thin film resistor. However, the protection of generally used solder resist or the like has been described. Forming the film does not hinder the effects of the present invention. Further, the formation of the inorganic protective film on the resistance film does not disturb the effect of the present invention.

  Furthermore, in the third embodiment, the resin protective film is formed on the resistance film, but even if a protective film is further formed on the sheet substrate including the resin protective film, the effect of the present invention is not hindered. .

  Moreover, although the case where the exothermic element was a thin film resistance was demonstrated from 1st Embodiment to 3rd Embodiment, this invention is not limited only to thin film resistance. For example, as shown in FIG. 5, the exothermic element that is a thin film element may be an inductor element. FIG. 5 is a plan view and a cross-sectional view for explaining the configuration of the sheet-like circuit board 70 in the case where the heat generating element is an inductor element. 5A is a plan view, and FIG. 5B is a cross-sectional view taken along the line CC shown in FIG. 5A.

  In the case of the sheet-like circuit board 70, a heat radiation film 74, a first heat conductive film 76, and an inductor element 78 are formed in this order on the sheet substrate 72. The inductor element 78 includes terminal portions 82 and 84 and a coil portion 80 connected to these terminal portions. The terminal portion 82 is connected to the wiring electrode 86 via a jumper wire 88, and the other terminal. The part 84 is directly connected to the wiring electrode 86. The coil portion 80 and the terminal portions 82 and 84 are formed of the same conductor film. The first heat conductive film 76 has the same outer shape as the inductor element 78, while the heat radiation film 74 is formed in a larger area than the first heat conductive film 76.

  With this configuration, the sheet-like circuit board 70 is formed with the first heat conductive film 76 that is a hard and insulating thin film only in the lower region of the inductor element portion. Maintains flexibility. Moreover, the heat generated by the inductor element 78 is transferred not only to the first heat conductive film 76 in the lower region of the coil part 80 but also to the first heat conductive film 76 between the adjacent coil parts 80. Further, this heat is conducted from the first heat conductive film 76 to the entire surface of the heat radiation film 74, and as a result, the heat radiation film 74 has a relatively uniform temperature rise over the entire surface. As a result, infrared rays accompanying the temperature rise are radiated from the entire surface of the heat radiation film 74 through the sheet substrate 72, so that heat can be radiated efficiently.

  Note that the sheet-like circuit board 70 provided with the inductor element shown in FIG. 5 can be manufactured by substantially the same method as the manufacturing method described in the first embodiment, and thus the description thereof is omitted. Further, FIG. 5 shows a configuration in which a resin protective film for protecting the inductor element 78 is not formed, but a resin protective film as described in the third embodiment may be formed.

  Further, in the sheet-like circuit board 70 provided with the inductor element shown in FIG. 5, since the terminal portion 82 is surrounded by the coil portion 80, the wiring electrode 86 formed on the surface of the sheet substrate 72 using the jumper wire 88. However, it is not limited to such a connection method. That is, a wiring electrode formed on the sheet substrate 72 by forming an insulating layer on the surface including the terminal portion 82 and the coil portion 80, forming an opening in the insulating layer on the terminal portion 82, and then forming an upper wiring layer. You may connect with. When the insulating layer is formed as described above, a structure in which heat is radiated through the sheet substrate as shown in FIG. 5 is particularly effective.

  Furthermore, in the first to third embodiments, the thin film resistor and the inductor element have been described as examples. However, the present invention is not limited to these elements. For example, when the capacitor element generates heat in a high frequency circuit or the like, the configuration of the present invention may be applied using the capacitor element as a heat generating element. In the first to third embodiments, the sheet-like circuit board provided with individual heat generating elements has been described by taking a thin film resistor or an inductor element as an example. However, the present invention is not limited to this. For example, even a sheet-like circuit board having a circuit configuration including one or more thin film resistors, inductor elements, capacitor elements, and the like can be manufactured by the same configuration and manufacturing method as described above.

  The sheet-like circuit board of the present invention can increase the rated power by radiating and radiating heat generated by a heat-generating element that generates heat by energization among thin film elements formed on a resin-made sheet substrate. In addition, a highly reliable sheet-like circuit board having a high degree of design freedom can be obtained, which is useful in the field of portable electronic devices such as mobile phones.

(A) Top view which shows an example of a structure of the sheet-like circuit board concerning the 1st Embodiment of this invention (b) The sectional drawing (A) The top view for demonstrating the structure of the sheet-like circuit board concerning the 2nd Embodiment of this invention, (b) The cross-sectional view (c) The CC cross-sectional view Sectional drawing for demonstrating the structure of the sheet-like circuit board concerning the 3rd Embodiment of this invention. Sectional drawing for demonstrating another structure of the sheet-like circuit board concerning the embodiment (A) The top view for demonstrating the structure of the sheet-like circuit board about the case where a heat generating element is an inductor element in the 1st Embodiment of this invention in 3rd Embodiment. Figure

Explanation of symbols

10, 30, 50, 60, 70 Sheet circuit board 12, 32, 72 Sheet board 14, 34 Resistance film 16, 36 Wiring pattern 16a, 16b, 36a, 36b Connection electrode 18, 38, 76 First thermal conductive film 20, 42, 74 Thermal radiation film 22, 24 Thin film resistor (heat generating element)
40 Second heat conductive film 44, 46 Resin protective film 78 Inductor element 80 Coil part 82, 84 Terminal part

Claims (7)

A sheet substrate made of a resin that transmits infrared light;
A thin film element formed on the sheet substrate;
Including a heat-generating element that generates heat when energized among the thin-film elements and a thin-film layer for heat dissipation provided between the sheet substrate,
The heat dissipation thin film layer is formed in contact with the heat-generating element, and a heat radiation film formed in contact with the sheet substrate and having a shape at least larger than the first heat conductive film. The first heat conductive film is an insulating film having at least the same shape as the heat-generating element, and the heat radiation film is in the infrared light transmission range of the sheet substrate. A sheet-like circuit board characterized by using a material having a greater emissivity than that of a heat conductive film. The exothermic element is a thin film resistor;
The first heat conductive film is formed in contact with the resistance film of the thin film resistor, has the same shape as the resistance film, and has a thickness larger than the resistance film and thinner than the connection electrode connected to the resistance film. The sheet-like circuit board according to claim 1. The exothermic element is a thin film resistor;
The thin film layer for heat dissipation further includes a second heat conductive film having a shape larger than that of the first heat conductive film between the first heat conductive film and the heat radiation film. The sheet-like circuit board according to claim 1, wherein the shape is equal to or greater than the shape of the second heat conductive film. A resin protective film that covers the heat generating element is formed on the heat generating element, and the emissivity in the infrared light range of the resin protective film is at least larger than the emissivity of the first heat conductive film. The sheet-like circuit board according to claim 1, wherein the sheet-like circuit board is used. A step of roughening the surface of a sheet substrate made of a resin that transmits infrared light;
On the roughened sheet substrate, a thermal radiation film having an emissivity at least larger than an emissivity of the first thermal conductive film in an infrared light transmission range of the sheet substrate, and the first thermal radiation film on the thermal radiation film Forming a thin film layer for heat dissipation formed by laminating the heat conductive film of
Forming a heat-generating element on the first thermal conductive film. A method for manufacturing a sheet-like circuit board. As the heat radiation thin film layer, a second heat conduction film having a shape larger than the first heat conduction film is further formed between the first heat conduction film and the heat radiation film, 6. The method for manufacturing a sheet-like circuit board according to claim 5, wherein the shape is formed to be equal to or greater than the shape of the second heat conductive film. The resin protective film having an emissivity in an infrared light range equal to or higher than the thermal emissivity of the first thermal conductive film is further formed so as to cover the exothermic element. 7. A method for producing a sheet-like circuit board according to 6.

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